Currently, reduced pressure drying device has two arrangements of vent holes: one is central ventilation arrangement; the other is peripheral ventilation arrangement. However, as to large-sized substrates, both the two arrangements will cause non-uniform ventilation due to a small number of vent holes and distribution thereof. Further, due non-uniform gas flow over a substrate surface caused by poor fluidity of photoresist and humidity difference on the substrate surface, etc., speckles—most commonly crescent-like speckles—will appear after reduced pressure drying. Currently, the speckles after reduced pressure drying can not be effectively controlled, which increases false rate in substrate quality judgement, and is adverse to substrate quality inspection, thus affecting substrate quality and causing inconvenient for subsequent operations.